swift optionals in go? tcard/sgo#27

1_playground.swift

// 1. Like SGo

var regularVar: String

// This will _not compile_.
// print(regularVar)

// This will _not compile_.
// regularVar = nil

regularVar = "value"

print(regularVar) // "value"
print(type(of: regularVar)) // "String"

2_playground.swift

// 2. Like SGo with ?

var optionalWrappedVar: String?

print(optionalWrappedVar) // "nil"
print(type(of: optionalWrappedVar)) // "Optional<String>"

// This will crash during runtime.
// print(optionalVar!)

optionalWrappedVar = nil
optionalWrappedVar = "value"

print(optionalWrappedVar) // "Optional("value")"

// Now that it has a value, it will not crash when unwrapped.
print(optionalWrappedVar!) // "value"
print(type(of: optionalWrappedVar!)) // "String"

// But the use of ! remains crash prone, so unwrap with an expression.
if let unwrappedVar = optionalWrappedVar {
	print(unwrappedVar) // "value"
	print(type(of: unwrappedVar)) // "String"
} else {
	// nil.
}

3_playground.swift

// 3. Like Go (or perhaps SGo with !)

var implictlyUnwrapperOptionalVar: String!

// This will crash during runtime.
// print(implictlyUnwrapperOptional)

implictlyUnwrapperOptionalVar = nil

implictlyUnwrapperOptionalVar = "value"

print(implictlyUnwrapperOptionalVar) // "value"
print(type(of: implictlyUnwrapperOptionalVar)) // "ImplicitlyUnwrappedOptional<String>"

if let unwrappedVar = implictlyUnwrapperOptionalVar {
	print(unwrappedVar) // "value"
	print(type(of: unwrappedVar)) // "String"
} else {
	// nil.
}